The present invention relates to a high reliability, low-noise, pressurized fluid control system and, more particularly, to a system of one or more modular servo valves operated individually or in groups by a central controller to supply any desired fluid pressure to a hydraulic actuator aboard a submarine or other marine vessel.
Submarines and other ocean going vessels currently utilize a centralized hydraulic power plant which supplies fluid power to a plurality of actuators located throughout the ship. Each actuator performs a specific function, and the power requirements of each varies widely with the application. For example, ram movements in a typical sea water valve actuator may require less than 10 gal/min, while those in an actuator connected to a control surface such as a diving plane or rudder may require over 100 gal/min.
To ensure that a critical component remains operable despite extensive equipment damage or failure, shipboard hydraulic systems generally incorporate some level of redundancy. For example, flood control systems, installed where seawater pipes enter or leave a submarine's power pressure hull, typically employ redundant hydraulic circuits each consisting of a fluid reservoir, pump, and supply/return lines for supplying fluid to an actuator. The redundancy minimizes the effect of component failure in any one circuit so that the actuator is supplied with fluid at all times.
Control surface hydraulic systems, being similarly critical to ship safety, must be very reliable and therefore must presently be designed to include a significant level of redundancy. Typically, control surface rams receive fluid power from two sources via independent valves, in effect, from a normal servo valve (SV) and an emergency control valve (ECV). The SV and ECV are each constructed with the capacity to independently supply all of the pressurized fluid required, at the desired flow rate, to the actuator. Thus, if the SV or other component of the normal fluid supply system fails, a power transfer valve (PTV) in fluid communication with the SV and ECV continues to supply fluid power to the control surface ram by shifting from a normal mode to an emergency mode. In shifting to the emergency mode, the PTV shuts a valve connecting it to the SV and opens a valve to the ECV, thereby maintaining the flow of needed fluid to the actuator.
The benefits of maintaining redundant "back-up" systems, however, is not without cost. In submarine systems, the expense of providing and maintaining duplicate systems for the control surface actuators is particularly large because they must meet large power requirements yet operate at very low noise levels.